1. Field of the Invention
The present invention relates to a semiconductor device with epitaxial structure and manufacturing method thereof, and more particularly, to a semiconductor device with epitaxial structure for selective strain scheme (SSS) and manufacturing method thereof.
2. Description of the Prior Art
Epitaxial structures are prevalently used in a wide variety of semiconductor applications. For example, the prior art usually forms epitaxial structures in a single crystal substrate by performing a selective epitaxial growth (hereinafter abbreviated as SEG) method. Since the epitaxial structures have the crystalline orientation almost identical to the crystalline orientation of the substrate, the epitaxial structures serves as a raised source/drain or a recessed source/drain for the semiconductor device. Because the lattice constant of the epitaxial structures is larger than that of the silicon substrate, a strain stress is generated to the channel region of the meta-oxide semiconductor (hereinafter abbreviated as MOS) transistor device. Accordingly, carrier mobility in the channel region is improved and the speed of the MOS transistor device is increased. By rendering strain stress to improve the carrier mobility, the epitaxial structures therefore serve as one approach of the selective strain scheme (SSS).
Although the epitaxial structures efficiently improve device performance, it increase complexity of the semiconductor fabrication and difficulties of process control. Furthermore, stress from epitaxial source/drain is required of being directly and efficaciously pointed to the channel region. And thus it also increases design and fabrication difficulties.
Accordingly, though the epitaxial structure is able to improve the device performance, it is always in need to provide semiconductor devices as expected when the progress of semiconductor manufacturing technology is improved and complexity of the products is increased.